Electrical timing device

ABSTRACT

An electrical timing device having at least one pair of timelimit switching contacts to be operated in response to respective first and second states of operation of an electromagnet device. This timing device is provided with a spring clutch assembly capable of permitting the rotation of a cam disc together with a driven gear driven by the motor unless otherwise the cam disc is obstructed and also for permitting the rotation of the driven gear independent of the rotation of cam disc, whereby change of the interval of a desired preset time during which the timing device is operated can be varied as desired.

United States Patent Nakama et al.

n51 3,693,119 51 Sept. 19,1972

[54] ELECTRICAL TIMING DEVICE 3,284,734 11/1966 Schleicher ..335/68 Inventors: Katuhiko Nakam. 92 K 3,611,216 Matsuo et al. monomiya, Oaza-Kautari,

Nagasaka-cho; Shunichi Agatahama, 'y Examiner-Harold Bloome 9, Kaidenuenocho, Nagaska-cho, Attorneys-Craig, Am0nne1li& Hill both of Otokuni-gun, Kyoto-fu, Japan [57] ABSTRACT [22] Filed: Sept. 16, 1971 An electrical timing device having at least one pair of time-limit switching contacts to be operated in App! 180895 response to respective first and second states of opera- [30] Foreign Application Priority Data tion of an electromagnet device. This timing device is provided with a spring clutch assembly capable of per- Sept 1970 Japan mitting the rotation of a cam disc together with a [52] US. Cl. ..335/59, 200/38, 335/68 driven gear driven by the motor unless otherwise the [51] Int. Cl. ..H0lh 7/14 cam disc is obstructed and also for permitting the [58] Field of Search ..335/65, 64, 63, 59, 68, 71, rotation of the driven gear independent of the rotation 53/395 of cam disc, whereby change of the interval of a desired preset time during which the timing device is [56] R f r n Cited operated can be varied as desired.

2,957,962 10/1960 l-lanstein et a1 ..335/74 3,190,976 6/ 1965 Ellis et a1. ..200/38 A m I I K 37! 3 z z 370 4 PATENTED 19 3.693, 1 l9 sum 1 0f 2 292.- 24a 29 29a 30a 27 24:,

INVENTORS KATUHIKO NAKAMA,

$HUNl -H\ AGATAHAHA BY 04% uionnlu i 4 ATTORNEYS ELECTRICAL TIMING DEVICE The present invention relates to an electrical timing device and, more particularly, to an electrical timing device of improved performance and simplified type wherein the provision has been made to permit the preset time to be adjustably varied even during the operation of the electrical timing device.

Heretofore, there has been proposed various types of timing device. Of these types, one exemplary type has been designed so as to be operated in such a manner that, while the drive gear is constantly driven by an electrical motor, the rotational power of the drive gear is transmitted to the driven gear by the clutching action in cooperation with the electromagnet and, immediately after the driven gear has been rotated through a certain angle of rotation, i.e., at the lapse of the preset time, a switching device for controlling an external circuit is operated.

In the timing device of such type, it is necessary to cut off the power transmission from the motor to the driven gear after the switching device has been operated. This is because, if this power transmission cut-off operation is neglected or fails, the motor will be subjected to an unbearable load which may result in breakage of the timing device itself, otherwise the malfunction of either the drive gear or the driven gear will occur.

There has also been proposed two conventional types of timing device provided with means for preventing the motor from being subjected to such an unbearable load; one of which is so designed that the electrical power supply to the motor is cut off immediately after the time-up moment while the other is so designed that the electrical power supply to the electromagnet is cut off immediately after the time-up moment for the purpose of forcibly disengaging the drive gear from the driven gear.

The timing device of the first mentioned conventional type is largely accepted because of its technical reliability and less frequent occurrence of the malfunction. However, there has been a drawback in that the timing device is bulky in size due to the provision of an additional switching mechanism for cutting off the U.S. Pat. application, supply to the motor and a large-size electromagnet necessary to operate said additional switching mechanism, resulting in an increase of the manufacturing cost.

On the other hand, even in the timing device of the second mentioned conventional type, for the purpose of forcibly disengaging the drive gear from the driven gear, it has been necessitated to provide therein an auxiliary lever operable for this purpose, which will result not only in a complicated construction, but also in an increase of the sizeof the electromagnet as well as the timing device itself.

To eliminate the above mentioned disadvantages inherent to the conventional electrical timing device, an improved one has been proposed such as disclosed in the pending U.S. Pat. application filed on Nov. 25, 1969 under Ser. No. 879,876 and now Pat. No. 3,611,216. According to this U.S.patent application, the electrical timing device is provided with means for preventing the electrical motor from being subjected to the unbearable load. This preventing means is in the form of a toothless portion formed along a portion of the periphery of the driven gear into which the drive gear drivingly connected with the electrical motor by way of the reduction gears can be engaged after the driven gear has been rotated through a predetermined angle of rotation, that is, after the lapse of the preset time, so that the drive gear run idle in said toothless portion.

In the electrical timing device of this patent application, although a built-in switch for cutting off the power supply to the motor has been provided in addition to the time-limit switch operable so as to control an external electrical device, the necessity to cut off the power supply to the motor has been substantially eliminated without the motor being subjected to the unbearable load and/or without either the drive gear or the driven gear being damaged. This is because, in view of the provision of the toothless portion formed along a portion of the periphery of the driven gear, the drive gear can run idle in said toothless portion once it falls into said portion after the lapse of the preset tine.

However, even in this proposed electrical timing device, there still remains a disadvantage, as has been common to most conventional electrical timing devices, in that the interval of desired, preset time cannot be changed during the operative period of the timing device. It has been well recognized that change of the interval during which the timing device is in operation is oftentimes necessitated, for example, when the time at which an external electrical device to be controlled thereby is to be operated is extended or advanced under a certain circumstance in which the user or operator of the timing device is placed. By way of example, assuming that the operator of the timing device wishes to switch on a lamp after the lapse of an hour, he will set the timing device so as to commence its operation an hour later. In the event that, after 20 minutes later then, situation compelles him to immediately switch on the lamp, he must advance the timing device to cancel the remaining period of time, say, 40 minutes, thereby to permit the lamp to be immediately switched on. On the contrary thereto, in the event that, after 50 minutes later then, another situation compelles him to delay the switching-on of the lamp for an additional 30 minutes, he must adjust the timing device to extend the remaining period of time, say, 10 minutes, thereby to permit the lamp to be switched on after the lapse of 40 minutes.

The both handling procedures as hereinabove described cannot be achieved in the conventional electrical timing device as well as such a timing device as disclosed in the pending U.S. Pat. application Ser. No. 879,876.

Accordingly, an essential object of the present invention is to provide an improved electrical timing device wherein means is provided to permit the change of interval during which the timing device is in operation so that the time-up moment can be extended or advanced.

Another object of the present invention is to provide an improved electrical timing device wherein means is provided to prevent the drive motor from being subjected to an unbearable, excessive load even if the electrical power supply to the motor continues upon expiration of the preset time.

A further object of the present invention is to provide an improved electrical timing device wherein means to permit the advancement or the extension of the time-up moment of the timing device and means to prevent the drive motor from being subjected to an unbearable, excessive load are formed into a single mechanical clutch system.

A still further object of the present invention is to provide an improved electrical timing device which can be manufactured at low cost with substantial reduction of the size thereof without accompanying any loss of operative accuracy.

According to the present invention, a spring clutch is provided in the electrical timing device as including a rotary member formed with a notch along a portion of the periphery thereof and a spring member snugly interposed between said rotary member and the driven gear. This spring clutch acts to permit the rotation of the rotary member together with the rotation of the driven gear driven by an electrical motor until the timelimit switch is closed and to permit the rotation of the only driven gear even after the time-limit switch has been closed.

By the provision of this spring clutch, it can be ad vantageously eliminated to use different mechanisms for different functions of various parts of the timing device. Accordingly, it is clear that the timing device of this kind can be simplified in size and manufactured at low cost. without necessitating any complicated manufacturing processes.

These and other objects and features of the present invention will become apparent from the following description taken in conjunction with a preferred embodiment shown in the accompanying drawings, in which;

FIG. 1 is a longitudinal sectional view of an electrical timing device constructed in accordance with the teachings of the present invention,

FIG. 2 is top plan view of FIG. 1 with a portion being broken away to show the interior of the timing device,

FIG. 3 is a longitudinal sectional view, on an enlarged scale, of an essential portion of the timing device shown in FIG. 1 incorporating the features of the present invention, the other portion being schematically shown, v

FIG. 4 is a perspective view, on an enlarged scale, of a cam disc employed in the timing device, and

FIG. 5 is a schematic front view of a knob construction employed in the timing device.

Referring first to FIGS. 1 and 2, an electrical timing device as shown generally comprises a casing of substantially square cross-section, as indicated by 10, and having one end open to the outside and the other end formed with a circular opening a through which a dial assembly 11 is adapted to project to the outside as will be mentioned later. The open end of the casing 10 opposite to the circular opening 10a is adapted to be closed by a stem plate 12. This stem plate 12 is integrally provided at its exterior side with a plurality of electroconductive pins 12a for outside connection with a suitable electric circuit to be operated by the electrical timing device of the present invention and rigidly fastened to the casing 10 by means of a plurality of screws 13 in the assembled condition.

Extending from the four corners of the stem plate 12 toward the interior of the casing 10 is the corresponding number of studs 13, each having one end rigidly connected with the corresponding corner of the stem plate 12 and the other end connected with the corresponding corner of a first partition plate 14. The first partition plate 14 defines a gear box 15 in cooperation with a second partition plate 16 spaced therefrom by means of a plurality of stud members 17 rigidly connecting therebetween, said gear box 15 accommodating therein a plurality of gears which constitute a reduction gear unit as generally indicated by 18.

An electrical drive motor 19 is fixedly accommodated in a spacing defined between the interior side of the stem plate 12 and the first partition plate 14 and having its drive shaft situated within the gear box 18 and drivingly connected with one of the gears of the reduction gear unit 18. The rotational force of the motor 19 can be transmitted to a driven gear 20, which is rotatably supported as will be mentioned later, through a shaft 21. This shaft 21 has one end rotatably journalled by the first partition plate 14 and mounted rigidly with a gear connected with the drive shaft of the motor 19 through the reduction gear unit 18, and the other end rigidly mounted with a pinion 21a engageable with said driven gear 20. This shaft 21 is constantly downwardly urged by means of a substantially V- shaped elastic member 22 with the pinion 21a directed toward the driven gear 20, said elastic member 22 having its apex portion in contact with an intermediate portion of the shaft 21 through a grooved roller 23 rotatably mounted on that portion of the shaft 21 and its two coiled ends rigidly connected with an upper edge of the second partition plate 16.

There is provided a substantially L-shaped frame 24 in a spacing defined between the second partition plate 16 and the other end of the casing 10 where the circular opening 10a is formed. This L-shaped frame 24 is formed with an upstanding plate 24a and a bottom plate 24b horizontally extending substantially at right angles to said upstanding plate 24a, said bottom plate 24b being integrally formed with a pair of plugs 24c extending behind the root of the upstanding plate 24a. The L-shaped frame 24 is supported in position with the upstanding plate 24a secured to the second partition plate 16 by means of fastening members such as fiat-headed screws 25 while the bottom plate 24b is fixedly mounted with an electromagnet 26.

Horizontally positioned above the electromagnet 26 is a movable iron member 27 having a pair of spaced lugs 27a extending behind the second partition plate 16 through respective notches formed along the both side edges of said second partition plate 16 and situated above the corresponding lugs 240 of the L-shaped frame 24. This movable iron member 27 is pivotable through a definite angle of rotation about the notches 16a formed along the both side edges of the second partition plate 16 and normally pivoted in the direction away from the electromagnet 26 by means of a pair of tension springs 28 operatively suspended between the lugs 240 of the frame 24 and the lugs of the iron member 27, respectively. Only when the electromagnet 26 is excited, this movable iron member 27 can be attracted close to the electromagnet 26 against the action of each of the tension springs 28.

The arrangement so far described is substantially the same as disclosed in the pending US. Pat. application under Ser. No. 879,876, and now US. Pat. No. 3,61 1,216, assigned to the same assigee and, therefore,

the details of construction of the arrangement hereinbefore described are somewhat omitted. The present invention is essentially directed to the remaining portion of the timing device which will be hereinafter fully described particularly with reference to FIG. 3 through FIG. 5. However, it is to be noted that, during the operation of the timing device herein proposed, both the motor 19 and the electromagnet 26 should be respectively in the operative condition.

Referring now to FIG. 3 in which the remaining portion of the electrical timing device that has not yet described is shown, the movable iron member 27 is mounted on its upper surface with a fixed supporter 29 having a pair of bearing pieces 29a spaced a distance from each other. This fixed supporter 29 is adapted to carry a substantially Y-shaped member 30 having a pair of enlarged ends 30a and the other tapered end 30b formed with a downwardly projected feeler piece 30c of which the function will be mentioned later. This Y- shaped member 30 is pivotally mounted on the fixed supporter 29 by means of an elongated pin 31 having its both ends rigidly journalled by the bearing pieces 29a of the fixed supporter 29 and loosely extending through the pair of the enlarged ends 30a of the Y-shaped member 30.

The Y-shaped member 30 is normally urged about the elongated pin 31 in the same direction as the movable iron member 27 pivots upon excitation of the electromagnet 26, by means of a torsion spring 32 having a pair of outside ends lying on the upper surface of the Y- shaped member 30 and an intermediate end in contact with or secured to a suitable portion of the fixed supporter 29. This torsion spring 32 herein employed is in the form that a pair of coiled spring portions are provided between each of the outside ends and the intermediate end substantially as shown. However, other than this form of torsion spring, a torsion having a single coiled portion or a leaf spring may be employed for the same purpose.

As clearly shown in FIG. 2, the pair of the enlarged ends 30a of the Y-shaped member 30 are respectively provided with movable contact bars 33a and 33c, each having one end secured to the corresponding one of the enlarged ends 30a and serving as a terminal for outside electrical connection through the corresponding one of the pin 12a and the other end formed into a contact point 33b or 33d.

The fixed supporter 29 is also formed at its intermediate portion with a stopper 29b vertically extended therefrom for restricting a further rotation of the shaft 21 by the action of the V-shaped elastic member 22, the height of which is selected such that, when the iron member 27 is in the electromagnetically attracted condition, the shaft 21 permits the pinion 21a to be snugly engaged with the driven gear 20.

Reference numeral 34 indicates a front plate of square shape having an circular projection 3.4a adapted to project toward the outside through the circular opening a of the casing in the assembled condition. This front plate 34 is provided with a pair of fixed contact members 35a and 35c having respective contact points 35b and 35d, each of said fixed contact members 35a and 350 being rigidly connected at one end with the adjacent end of the corresponding one of supporter strips 36a and 36b, each of which has the other free end secured to the interior side of.the front plate 34 and serves as a terminal for outside electrical connection through the corresponding one of the pins 12a. Another pair of fixed contact members 37a and 37c having respective contact points 37b and 37d and respective terminals (not shown) for outside electrical connection through the corresponding ones of the pins 12a are similarly secured to the interior side of the front plate 34 at a position beneath the first mentioned pair of the fixed contact members 35a and 35c. However, it is to be noted that such elements as indicated by 35b, 35d, 37c and 37d are invisible and, therefore, these elements are not shown in the drawings although the respective reference numerals are given for a clear understanding of the description of the present invention.

The circular projection 34a of the front plate 34 is formed at its substantially central portion with a bore 34b through which a spindle 38 is rotatably extended. This spindle 38 has one end situated outside the front plate 34 and rigidly connected with a pointer needle 39 and the other end situated within the casing 10 and rigidly mounted with a spring clutch assembly.

The spring clutch assembly comprises a bushing 40 formed with a flange 40a at one end thereof adjacent to the front plate 34 and rigidly connected with a substantially intermediate portion of the spindle 38, a flanged cam disc 41 rigidly mounted on one end extremity of said spindle 38 opposite to the other end extremity mounted with the pointer needle 39, and a resilient member 42 loosely disposed around the spindle 38 at a position between said cam disc 41 and the driven gear 20 freely rotatably mounted on said bushing 40, said resilient member 42 being, in the instance as shown, employed in the form of a compression spring. The flanged cam disc 41 is formed with a cut-out portion 41a as clearly shown in FIG. 4 along a portion of the peripheral flange thereof, said cut-out portion being adapted to receive therein the feeler piece 30c of the Y-shaped member 30 as will be mentioned later.

The spring clutch assembly of the construction as hereinabove described is designed such that said flanged cam disc 41 and said driven gear 20 can be integrally rotatable in either direction unless otherwise the rotation of either the cam disc 41 or the driven gear 20 is obstructed and, once the rotation of either the cam disc 41 or the driven gear 20 is obstructed, the other element can undergo its rotation independent of that of the obstructed element. This can be achieved by suitably selecting the resiliency of the resilient member 42.

Disposed around the flange 40a of the bushing 40 is a spiral spring 43 having an inner end rigidly connected with a portion of said flange 40a and the other outer end rigidly connected with a suitable portion of the front plate 34 by which the spindle 38 is normally urged to rotate in one direction and, hence, the flanged cam disc 41 is also normally urged to rotate in one direction.

The circular projection 34a of the front plate 34 is provided at its outer peripheral surface with a threaded surface with a calibrated scale 45, as clearly shown in FIG. 5, of the horse shoe shape and also provided with a stopper 46 which may be of screw type for restricting the revolving movement of the pointer needle 39 at a predetermined position.

The knob 44 mannualy rotatable in either direction is provided at its substantially central portion with an index pointer 44a for indicating the preset time readable on the calibrated scale 45. This knob 44 is also formed on its interior side with a projection 44b engageable with a recess formed in the pointer needle 39 so that, when the knob 44 is rotated with its index pointer 44a indicating the preset time readable on the calibrated scale 45, the pointer needle 39 can be brought against the spiral spring 43 to the same position as indicated by the index pointer 44a.

This knob construction may be the same as disclosed in the pending, abovenumbered U.S. patent application. However, in practice, for the purpose of reduction of the number of the necessary parts for this knob construction, the annular ring 43 may be omitted. Instead thereof, the knob 44 is rotatably supported by the easing 10 with the right half of said knob 44 being projected outside through the circular opening 10a of the casing 10.

in the instance as shown, the timing device is designed such that the time setting can be appreciated by turning the knob 44 in the anticlockwise direction from a position where the pointer needle 39 is in contact with the stopper 46, the maximum interval of the preset time being obtainable when the pointer needle 39 is in the position abutted against the stopper 46 by the action of the spiral spring 43 urging the spindle 38 so as to rotate in the clockwise direction.

While the timing device of the present invention is constructed as hereinbefore fully described, the operation thereof will be hereinafter described.

Assuming now that the knob 44 is first turned accompanying the anticlockwise rotation of the pointer needle 39 against the action of the spiral spring 43 until said needle 39 indicates a desired, preset time readable on the calibrated scale 45 and, then, the motor 19 and the electromagnet 26 are concurrently brought into the operative conditions, respectively, the movable iron member 27 can be downwardly attracted by the electromagnet 26 against the composite action of the tension springs 28 thereby to permit the shaft 21 to downwardly move about its journalled end with the pinion 21a brought into mesh with the driven gear 20. At this time, the feeler piece 30c of the Y-shaped member 30 is still in contact with the peripheral flange of the cam disc 41 so that the pair of the contact points 33b and 33d are respectively in contact with the pair of the contact points 35b and 35d.

Upon engagement of the pinion 21a, that has been rotated by the motor 19 through the reduction gear unit 18, with the driven gear 20, the latter can be rotated in the anticlockwise direction, accompanying the rotation of the cam disc 41 and the bushing 40 in tight contact with the cam disc 41. At the same time as the cam disc 41 and the bushing 40 are integrally rotated, the pointer needle 39 commences its anticlockwise rotation against the spiral spring 43 until said pointer needle 39 is abutted against the stopper 46. During this operation, the index pointer 44a of the knob 44 remains at the position where it has been originally set with the pointer needle 39 indicating the desired, preset time readable on the calibrated scale 45.

Upon completion of the anticlockwise rotation of the pointer needle 39 at which time the cut-out portion 410 of the cam disc 41 is brought right below the feeler piece 30c of the Y-shaped member 30, the Y-shaped member 30 can be downwardly rotated about the pin 31 by the action of the torsion spring 32 so that the feeler piece 30c can fall into said cut-out portion 41a of the cam disc 41, thus obstructing the further rotation of said cam disc 41 while the pair of the contact points 33b and 33d of the movable contact bars 33a and 33c are respectively brought into contact with the pair of the contact points 37b and 37d thereby to complete a circuit of an external device to be operated by the timing device.

Even through the further rotation of the cam disc 41 is obstructed by the feeler piece 30c engaged in the cutout portion 41a of the cam disc 41, the driven gear 20 can be still rotated without the motor 19 being subjected to the excessive load. This is because the spring clutch assembly permits the rotation of the driven gear 20 independent of the rotation of the cam disc 41 while a slit occurs between the driven gear 20 and the adjacent end of the resilient member 42. To achieve this result, the resilient force exerted by the resilient member 42 and acting on the driven gear 20 should be selected so as to be smaller than the rotational force transmitted from the motor 19 via the pinion 21a, said rotational force being in turn smaller than the frictional force exerted between the driven gear 20 and the adjacent end of the resilient member 42. However, only when the electromagnet 26 is unexcited, disengagement between the pinion 21a and the driven gear 20 takes place, since the movable iron member 27 is upwardly moved by the action of the springs 28 about the notched portions 16a of the second partition plate 16 so that the stopper 29b of the fixed supporter 29 mounted on said member 30 pushes the shaft 21 in the upward direction about the journalled end of said shaft 21. Concurrently, disengagement between the feeler piece 300 of the Y-shaped member 30 and the cut-out portion 41a of the cam disc 41 takes place as the iron member 27 is upwardly moved as hereinbefore described. In this connection, an adjustable screw 30d threadably extended through the Y-shaped member 30 with its lowermost end in contact with the upper surface of the iron member 27 should be adjusted such that, when the iron member 27 is in the upwardly shifted position, the feeler piece 300 can be positioned a relatively smaller distance away from the peripheral flange of the cam disc 41. In other words, during the condition in which the iron member 27 is in the upwardly shifted position, the feeler piece 30c slightly clears off from the peripheral flange of the cam disc 41.

Upon disengagement of the feeler piece 300 from the cut-out portion of the cam disc 41, the latter can be automatically rotated in the reverse direction by the action of the spiral spring 43 and thus the pointer needle 39 can be returned, rotating in the clockwise direction, to the position where said pointer needle 39 is abutted against the stopper 44b of the knob 44, namely, the originally set position.

ln the event that, during the operation of the timing device as hereinbefore described, the interval of the preset time is desired to be changed, it is only necessary to turn the knob 44 in either direction. Since the spring clutch assembly is designed such that a slip occurs between the driven gear 20, which is at this time in mesh with the rotating pinion 21a, and the adjacent end of the resilient member 42 when the knob 44 is turned so as to cause the pointer needle 39 and thus the spindle 38 to rotate against a composite force of the value substantially equal to the resiliency of the spiral spring 43 plus the resilient force of the member 42 acting on the driven gear 20, the change of the interval of the preset time can be easily achieved without the motor being subjected to the excessive load.

it is to be noted that, in practice, while a combination of such elements as indicated by 33d, 35d and 37d serves as a double throw switch for operating the external circuit (not shown), a combination of such elements as indicated by 33b, 35b and 37b serves as a double throw switch which may be utilized to operate both the motor 19 and the electromagnet 26.

To ensure the tight contact between the contact point 33b or 33d to the contact point 35b or 35d, respectively, each of the fixed contact strips 35a and 350 must preferably have a sufficient resiliency acting so as to downwardly urge the fixed contact strip in the direction of the contact point 33b or 33d. However, this fixed contact strip 35a or 350 has its free end resting on a stopper 47 formed on the interior side of the front plate 34 as shown and substantially extending in the horizontal direction.

From the foregoing description, it is clear that, in addition to the various features obtainable from the disclosure of the pending, abovenumbered US. patent application, a further feature can be obtained in that the spring clutch assembly affords the change of the interval of the preset time.

Although the present invention has been fully described by way of example, various changes and modifications are apparent to those skilled in the art. For example, instead of the compression spring, a Belleville spring, spring washer or wave washer may be employed for the resilient member 42. In addition, various method such as utilizing a'plurality of screws may be contemplated for connection between the cam disk 42 and/or the bushing 40 with the spindle 45.

What is claimed is:

1'. In an electrical timing device comprising an electrically operated motor, a driven gear adapted to be driven by said motor, means for setting a desired preset time which includes a pointer needle mounted on a spindle and a dial knob operatively associated with said pointer needle, electromagnetic means for selectively permitting or preventingthe rotational power transmission from said motor to said driven gear, and at least one pair of time-limit switching contacts to be operated upon expiration of a preset time interval, the improvement comprising means operatively associated with said electromagnetic means and including a pivotable solid member having a feeler piece, said pair of said time-limit switching contacts being adapted to be operated in response to respective first and second states of operation of said feeler piece of said solid member, and a spring clutch assembly consisting of a rotary member formed with a cut-out portion substantially along a portion of the periphery thereof into which said feeler piece is engageable upon the expiration of said preset time interval, said rotary member being rigidly mounted on said spindle, and a resilient member loosely mounted around said spindle at a position between said rotary member and said driven gear for permitting the rotation of said rotary member together with said driven gear that has been driven by said motor so long as said feeler piece is in contact with the periphery of said rotary member and also for permitting the independent rotation of said driven gear, without accompanying the rotation of said rotary member, upon completion of the rotation of said pointer needle and thus said spindle through a certain angle of rotation determined by the desired preset time interval.

2. The timing device as claimed in claim 1, wherein said spring clutch assembly affords the change of the preset time interval even during an operative period of the timing device in which the latter is operating in accordance with the preset time that has been initially set.

3. The timing device as claimed in claim 1, wherein the resilient force exerted by said resilient member which acts on the driven gear is selected so as to be smaller than the rotational force transmitted to said driven gear from the motor, said rotational force being smaller than the frictional force exerted between said driven gear and the adjacent end of said resilient member during a period in which said feeler piece is in engagement with the cut-out portion of said cam disc.

4. The timing device as claimed in claim 1, wherein said resilient member of said spring clutch assembly comprises a compression spring.

5. The timing device as claimed in claim 1, wherein said rotary member is a flanged cam disc having a flanged portion along the periphery thereof and said resilient member is positioned while surrounded by said flanged portion of said cam disc.

6. The timing device as claimed in claim 1, wherein a spiral spring is further provided with its both ends rigidly connected with said spindle and a rigid fixed portion of said timing device, said spiral spring being adapted to enable said pointer needle to automatically return to the original position where said dial knob has been preset upon disengagement of said feeler piece from said rotary member.

7. An electrical timing device comprising an electrically operated motor, a driven gear adapted to be driven by said motor, means for setting a desired preset time which includes a pointer needle mounted on a spindle, a dial knob operatively associated with said pointer needle, and a spiral spring having its both ends respectively connected with said spindle and a rigid fixed portion of the timing device for enabling said spindle and thus said pointer needle to automatically rotate in one direction, an electromagnetic means for selectively permitting or preventing the rotational power transmission from said motor to said driven gear, at least one pair of time-limit switching contacts to be operated upon expiration of a preset time interval, means operatively associated with said electromagnetic means and including a pivotable solid member having afeeler piece, said pair of said time-limit switching contacts being adapted to be operated in response to permitting the rotation of said cam disc together with said driven gear that has been driven by said motor so long as said feeler piece is in contact with the peripheral flange of said cam disc and also for permitting the independent rotation of said driven gear, without accompanying the rotation of said cam disc, upon completion of the rotation of said pointer needle and thus said spindle through a certain angle of rotation determined by the desired preset time interval. 

1. In an electrical timing device comprising an electrically operated motor, a driven gear adapted to be driven by said motor, means for setting a desired preset time which includes a pointer needle mounted on a spindle and a dial knob operatively associated with said pointer needle, electromagnetic means for selectively permitting or preventing the rotational power transmission from said motor to said driven gear, and at least one pair of time-limit switching contacts to be operated upon expiration of a preset time interval, the improvement comprising means operatively associated with said electromagnetic means and including a pivotable solid membEr having a feeler piece, said pair of said time-limit switching contacts being adapted to be operated in response to respective first and second states of operation of said feeler piece of said solid member, and a spring clutch assembly consisting of a rotary member formed with a cutout portion substantially along a portion of the periphery thereof into which said feeler piece is engageable upon the expiration of said preset time interval, said rotary member being rigidly mounted on said spindle, and a resilient member loosely mounted around said spindle at a position between said rotary member and said driven gear for permitting the rotation of said rotary member together with said driven gear that has been driven by said motor so long as said feeler piece is in contact with the periphery of said rotary member and also for permitting the independent rotation of said driven gear, without accompanying the rotation of said rotary member, upon completion of the rotation of said pointer needle and thus said spindle through a certain angle of rotation determined by the desired preset time interval.
 2. The timing device as claimed in claim 1, wherein said spring clutch assembly affords the change of the preset time interval even during an operative period of the timing device in which the latter is operating in accordance with the preset time that has been initially set.
 3. The timing device as claimed in claim 1, wherein the resilient force exerted by said resilient member which acts on the driven gear is selected so as to be smaller than the rotational force transmitted to said driven gear from the motor, said rotational force being smaller than the frictional force exerted between said driven gear and the adjacent end of said resilient member during a period in which said feeler piece is in engagement with the cut-out portion of said cam disc.
 4. The timing device as claimed in claim 1, wherein said resilient member of said spring clutch assembly comprises a compression spring.
 5. The timing device as claimed in claim 1, wherein said rotary member is a flanged cam disc having a flanged portion along the periphery thereof and said resilient member is positioned while surrounded by said flanged portion of said cam disc.
 6. The timing device as claimed in claim 1, wherein a spiral spring is further provided with its both ends rigidly connected with said spindle and a rigid fixed portion of said timing device, said spiral spring being adapted to enable said pointer needle to automatically return to the original position where said dial knob has been preset upon disengagement of said feeler piece from said rotary member.
 7. An electrical timing device comprising an electrically operated motor, a driven gear adapted to be driven by said motor, means for setting a desired preset time which includes a pointer needle mounted on a spindle, a dial knob operatively associated with said pointer needle, and a spiral spring having its both ends respectively connected with said spindle and a rigid fixed portion of the timing device for enabling said spindle and thus said pointer needle to automatically rotate in one direction, an electromagnetic means for selectively permitting or preventing the rotational power transmission from said motor to said driven gear, at least one pair of time-limit switching contacts to be operated upon expiration of a preset time interval, means operatively associated with said electromagnetic means and including a pivotable solid member having a feeler piece, said pair of said time-limit switching contacts being adapted to be operated in response to respective first and second states of operation of said feeler piece of said solid member, and a spring clutch assembly consisting of a flanged cam disc formed with a cut-out portion substantially along a portion of the peripheral flange thereof, said cut-out portion being adapted to receive therein said feeler piece upon the expiration of said preset time interval, said cam disc being rigidly mounted on sAid spindle, and a compression spring loosely mounted around said spindle at a position between said cam disc and said driven gear for permitting the rotation of said cam disc together with said driven gear that has been driven by said motor so long as said feeler piece is in contact with the peripheral flange of said cam disc and also for permitting the independent rotation of said driven gear, without accompanying the rotation of said cam disc, upon completion of the rotation of said pointer needle and thus said spindle through a certain angle of rotation determined by the desired preset time interval. 